Work done is equal to force by distance; so you take the force exerted, in newtons, and multiply that by the direction it's moved (from the starting point in a line, not along the path it's taken.)
The acceleration due to gravity changes as we move away from Earth, and the expression for gravitational potential energy must reflect this change. The total energy of a system is the sum of kinetic and gravitational potential energy, and this total energy is conserved in orbital motion.
80% from burning fossil fuels
Length=l=160cm=1.6m
Frequency=85Hz
#1
Fundamental frequency be v
![\\ \sf\bull\longmapsto v=\dfrac{\nu}{2\ell}](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20v%3D%5Cdfrac%7B%5Cnu%7D%7B2%5Cell%7D)
![\\ \sf\bull\longmapsto v=\dfrac{85}{2(1.6)}](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20v%3D%5Cdfrac%7B85%7D%7B2%281.6%29%7D)
![\\ \sf\bull\longmapsto v=\dfrac{85}{3.2}](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20v%3D%5Cdfrac%7B85%7D%7B3.2%7D)
![\\ \sf\bull\longmapsto v=26.6Hz](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20v%3D26.6Hz)
#2
First we have to find wavelength
![\\ \sf\bull\longmapsto \lambda=\dfrac{c}{v}](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20%5Clambda%3D%5Cdfrac%7Bc%7D%7Bv%7D)
![\\ \sf\bull\longmapsto \lambda=\dfrac{3\times 10^8ms^{-1}}{26.6}](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20%5Clambda%3D%5Cdfrac%7B3%5Ctimes%2010%5E8ms%5E%7B-1%7D%7D%7B26.6%7D)
![\\ \sf\bull\longmapsto \lambda=0.112\times 10^8m](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20%5Clambda%3D0.112%5Ctimes%2010%5E8m)
![\\ \sf\bull\longmapsto \lambda=112\times 10^5m](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20%5Clambda%3D112%5Ctimes%2010%5E5m)
![\\ \sf\bull\longmapsto \lambda=1.12\times 10^6m](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20%5Clambda%3D1.12%5Ctimes%2010%5E6m)
Now..
Velocity be v
![\\ \sf\bull\longmapsto v=f\lambda](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20v%3Df%5Clambda)
![\\ \sf\bull\longmapsto v=26.5\times1.12\times 10^6m](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20v%3D26.5%5Ctimes1.12%5Ctimes%2010%5E6m)
![\\ \sf\bull\longmapsto v=29.68\times 10^6](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20v%3D29.68%5Ctimes%2010%5E6)
![\\ \sf\bull\longmapsto v=2.9\times 10^7m/s](https://tex.z-dn.net/?f=%5C%5C%20%5Csf%5Cbull%5Clongmapsto%20v%3D2.9%5Ctimes%2010%5E7m%2Fs)
10mph is the acceleration that u are looking for